Gas-turbo engines



Oct. 7, 1958 J. D. THORN ET'AL GAS-TURBO ENGINES Filed April 22, 1955 5 Sheets-Sheet 1 \IIZW v. M

Oct. 7, 1958 J. D. THORN *ETAL GAS-TURBO ENGINES 5 Sheets-Sheet 2 Filed April 22, 1955 lllllllllllllu Oct. 7, 1958 J. D. THORN ETAL 2,855,246

I GAS-TURBO ENGINES Filed April 22, 1955 5 Sheets-Sheet 4 I) Iii! U UIZ I Filed April 22, 1955 Oct. 7 1958 J. D. THORN ETAL 2,855,246

GAS-TURBO ENGINES 5 Sheets-Sheet 5 I lll United States Patent GAS-TURBO ENGINES James D. Thorn and Anthony V. G. Jaclkman, Lincoln, England, assignors to Ruston & Hornsby Limited, lLiucoln, England, a corporation of Great Britain Application April 2 2, 1955, Serial No. 503,205

4 Claims. (Cl. 30217) This invention relates to open-cycle gas-turbo-engines, that is to say to turbo-engines in which the turbine(s) proper is (are) driven by air which having been drawn from the atmosphere and passed through a compressor is greatly expanded in volume by combustion with a fuel in a combustion chamber. Gas-turbo-engines may be designed to operate on various fuels; and the present in vention is particularly concerned with, the use of solid fuels in powdered form, especially peat.

In any design of equipment for burning powdered fuel in a gas-turboengine there are two fundamental requirements that must be satisfied; firstly, the fuel must be introduced to the combustion chamber, where the air is already at a high pressure, with the minimum of loss of the high-pressure air from the system; and secondly the control of the rate of supply of the fuel to the combustion chamber must be both precise and prompt. Thus the satisfaction of these requirements at least must be included among the objects of the present invention. Furthermore, the control of the flow of the fuel into the combustion chamber is desirably to be achieved without the introduction of pulsations into the fuel flow.

In our oopending patent application No. 503,203, we have described an arrangement for feeding powdered fuel such as peat to the combustion chamber of the engine in which the powdered fuel is fluidized and is passed through two fluidizing columns in series, the first working at atmospheric pressure, and the second at a pressure appropriate to the feeding of the fluidized fuel into the combustion chamber wherein of course a high pressure prevails. Such an arrangement is hereinafter referred to as a two-stage fluidization arrangement.

It is an object of the present invention to provide improved means of controlling the feeding of fluidized solid fuel such as peat to the combustion chamber.

The invention in one of its aspects consists in a twostage arrangement for the supply of fluidized fuel to the combustion chamber 'of a gas-turbo-engine in which the supply of fluidized fuel from the atmospheric fluidizing column to the pressurized fluidizing column is controlled in accordance with the level of the fluidized fuel in the pressurized column.

Various means may be used for determining the height of the fluidized bed in the pressurized column. Thus advantage may be taken of the electrical conductivity of the fluidized bed; electrodes may be fixed at different heights within the column so that when they are immersed in the bed they will be in effect grounded; such grounding of an electrode can readily be determined.

Again the pressure drop of the fluidizing air in its passage through the bed may serve to indicate the height of the bed.

In any case the means responsive to the height of the fluidized bed is used to control the setting of the outlet valve from the atmospheric fluidizing column, or to control the operation of the pump which is arranged between the outlet of the one column and the inlet of the other.

Patented Oct. 7, 1958 However, in one embodiment of the invention the pump was of a kind which operated at a constant speed but with I a volumetric efficiency determined by the setting of whatever valve might be arranged on its inlet side; in such a case it was the outlet valve of the first fluidizing column that was controlled.

The following description relates to the accompanying drawings, which show one embodiment of the invention by way of example only. In the drawings:

Figure 1 is a diagram of a peat-fired gas turbine embodying the invention;

Figure 2 is a diagram showing more particularly the electrical and hydraulic control circuitry pertaining to the turbine of Figure 1;

Figure 3 is a section through the valve controlling fuel-flow from the pressurized fluidizing column to the combustion chamber;

Figure 4 is a section through the valve controlling fuel-flow from the atmospheric fluidizing column to the pressurized column;

Figure 5 is a section through the valve controlling fuel flow from a source to the atmospheric column; and

Figure 6 is a section through the valve controlling the supply of fluidizing air to the pressurized column.

The complete engine As shown in Figure l of the drawings, the peat is fed in from a de-watering press (not shown) to a disintegrator 11 where it is broken into moderately small lumps. Thence it passes to a rotary louvre dryer 12 where it is dried by the exhaust of the engine, the exhaust being fed in from a conduit 13 and passing out through a conduit 14. The peat leaves the dryer 12 by falling onto a rotary table 15 where it is divided into two parts: one part is withdrawn to a mix-back conveyor 16 and is fed back to the tie-watering press (not shown), and the other part proceeds forwardly through conduit 17 to a grinding machine: both of these feeds are controlled by adjustable blades 18 on the rotating table 15. The grinding machine or attritor 19 is air swept, the air being introduced to the conduit 17 from a branch pipe 20. On leaving the attritor 19 the pulverized fuel is separated from the carrying air in a cyclone 21.

The cyclone 21 is arranged on top of an atmospheric fluidizing column 22 which acts as a storage vessel. From the fluidizing column 22 the peat flows into the peat pump 23 which with a supply of high pressure air fed through pipe 24 performs the function of pressurizing the peat supply. From the pump 23 the fluidized peat flows along conduit 25 to a small cyclone 26 which is arranged on top of a pressurized fluidizing column 27 and which separates the high pressure air from the peat carried by that air. From the pressurized fluidizing column 27 the peat is delivered through a valve 28 and conduit 29 to the combustion chamber 30 of the turbine 31.

The high-pressure air from the small cyclone 26 is taken over conduit 32 to the combustion chamber 30. The fluidizing air supply 33 for the low-pressure column 22 is obtained from some convenient source which may be external of the engine. Fluidizing air for the highpressure column 27 is obtained from the compressor 34 of the engine 31 via a booster fan 35 leading to conduit 36 and thence downwardly to the bottom inlet duct to column 27. Also a stream of air upwardly from the duct 36 serves both to carry the fluidized peat from the control valve 28 into the combustion chamber through duct 29, and to carry through the same duct 29 the outflow from an open connection 32, 37 coming from the top of the high-pressure fluidizing column 27.

The control circuitry Figure 2 of the drawings shows the electrical and hydraulic control circuitry pertaining to the engine of Figure 1.

.Fuel outflow from pressurized column From .the engine-speed governor 38, an oil-pressure line 39 leads to the valve 28 which controls the delivery of fuel from the pressurized fluidizing column 27 to the combustion chamber 30. This valve 28, which is shown in more detail in Figure 3, is a throttle valve, of which the degree of opening is dependent on the oil pressure in line 39, in turn dependent on the engine speed as marked by governor 38. Thus the outflow from the pressurized fluidizing column 27 to the combustion chamber 30 is controlled by valve 28 itself controlled in accordance with engine speed.

Fuel flow from atmospheric column to pressurized column The level of fluidized fuel within the pressurized column 27 is to be maintained between lower and upper limits, as determined by the heights of two electrical probes, a lower probe and an upper probe 41 as in Figure 2. These two probes are connected to a doubleacting relay 42, that is to say a relay which can be set in either of two positions, contacts open or contacts closed, by a current in the appropriate sense, and which then remains in the position as set, despite the cessation of current, until the application of a current in the opposite sense. The possibility of applying current in opposite senses to the relay 42 from the probes 40 and 41 has been represented by wires leading from the probes to the opposite ends of the relay coil: but this is merely a diagrammatic representation and does not necessarily represent the actual coil connections. A rise in the level of fluidized fuel in column 27 until it reaches the upper probe 41 causes the relay 42 to open its contacts; thereafter, and despite a fall in the level below the upper probe, the contacts remain open; only when the level falls below the lower probe 40 does the relay operate to close its contacts.

Closure of the contacts of relay 42 operates a solenoid valve 71 to close that valve.

Now the flow of fluidized fuel from the atmospheric column 22 to the'line 25 is controlled by a three-position valve 43, which is shown in greater detail in Figure 4. This valve 43 has an operating piston 44 and an obturating member 45 linked with the piston. obturating mmeber are urged upwardly by a spring 46. The cylinder 47 containing the piston 44 is permanently connected at its top end to an oil pressure line 48. At three different heights in the cylinder wall are drain connections 49, 50 and 51. The uppermost drain connection 49 includes a solenoid valve 52 which, if it be open, provides a leakage path for the pressure oil with the piston 44 in its uppermost position to which it is raised by the spring 46. On the other hand, if the valve 52 be closed then the piston 44 will be forced downwardly until the second drain conection 50 is uncovered. It is this drain connection that contains the solenoid valve 71; so that if this valve be open, the piston will be stayed at that intermediate position; on the other hand if the valve 71 be closed, the piston 44 will continue its downward displacement until the drain connection 51, which is permanently open, is exposed.

These three possible settings of the piston 44 result in three possible settings of the obturating member 45 in relation to aligned ports 53 through which fuel may flow; in the uppermost position the ports 53 are cut off from each other so that no fuel can flow; in the intermediate position a small aperture 54 in the obturating member 45 permits a restricted flow of fuel from the atmospheric column 22 to the pressurized column 27; while in The piston and the lowermost position, a large aperture 55 permits a full flow of fuel.

Thus an arrangement is provided in which the supply of fluidized fuel from the atmospheric fluidizing column to the pressurized fluidizing column is controlled in accordancewith the level of the fluidized fuel in the pressurized column.

Supply of fuel to atmospheric column The supply of fuel to the atmospheric column 22is controlled in accordance with the height of the fluidized bed in that column, this height being measured by the static pressure difference between the dilute phase and the bottom of the bed. This static pressure difference is represented diagrammatically as being developed in two pneumatic leads 56 which are connected to opposite side of a diaphragm chambre in an attritor feeder control unit 57, shown in greater detail in Figure 5.

The diaphragm 58 controls by its setting the build-up of oil pressure within a cylinder 59, and hence the setting of a piston 60 in that cylinder. This piston 60 determines the setting of the adjustable blades 18 (Figure 1) by which the rate of delivery of fuel to the atmospheric column is determined.

Thus the supply of fuel to the atmospheric column 22 is controlled by the height of the bed in that column; the height of the bed in that column is determined by the outflow therefrom and hence by the level in the pressurized column; and the level in the pressurized column is controlled by its outflow, and hence by the engine speed.

Supply of fluidizing air to pressurized column The supply of fluidizing air to the pressurized column 27 is derived from the main engine compressor 34, being taken off from the stream 36 along a pipe 61.

Now, the turbine cycle is such that the compressor speed automatically adjusts itself to the engine load; an increase in load produces an increase in speed resulting in an increase in both delivery pressure and temperature; a decrease in load gives the inverse. Therefore, velocity variations would occur in the fluidizing column with change of load, unless a control valve were used in the fluidizing air line.

Accordingly, in the pipe 61 is arranged a self-regulating throttle valt e 62, immediately up stream from a venturi 63. The venturi throat pressure, at 64, and the down-stream pressure, at 65, are fed to a diaphragm chamber on either side of a diaphragm 66. The diaphragm 66 actuates a hydraulic servo valve 67 which controls the throttle valve 62. The diaphragm is biased to some predetermined load by a spring 68 (Figure 6).

An increase in engine load momentarily increases the pressure drop across the venturi 63 above its value necessary to balance the biased spring load 68. This causes the hydraulic valve 67 to open a bleed in the valve 62 and throttle the fluidizing air supply until diaphragm balance is again restored. The procedure is reversed on a load reduction.

Maintaining the pressure drop across the venturi constant does not maintain the velocity exactly constant, but it is close enough for practical purposes.

in the valve as shown in Figure 6 it will be noted that there is an additional out of balance force on the diaphragm 66 due to the attachment of valve 69, reducing the effective area on this side of the diaphragm. This out of balance force acts as a compensating device and gives an even closer constant velocity characteristic.

It will be understood that the invention may take other forms: thus the supply of fluidized fuel from the atmospheric column to the pressurized column may be controlled in accordance with the pressure drop of the fluidizing air in its passage through the bed, that is to say, in the same manner as is controlled the supply of fuel to the atmospheric column.

What we claim is:

1. A system providing a stream of fluidized powdered fuel at high pressure comprising, a first fluidizing column, means introducing a stream of fluidizing air into said column at the bottom thereof, means feeding powdered fuel into said column at substantially atmospheric pressure, a second fiuidizing column, means including a source of high-pressure air for introducing fluidizing air into said second column at the bottom thereof, pumping means for feeding fluidized fuel from said first column into said second column at a pressure substantially higher than atmospheric pressure, a valve controlling the flow of fluidized fuel from said first column to said second column, sensing means for sensing the level of fluidized fuel in said second column, and control means controlled by said sensing means to operate said valve and maintain said level within a predetermined range.

2. A fuel supply system according to claim 1 wherein said sensing means comprises a pair of level-sensitive probes extending into said second column at the limits of said range.

3. A fuel supply system according to claim 1 wherein said control means for operating said valve comprises a cylinder containing a piston connected to operate said valve, said cylinder being connected to a source of fluid under pressure, a drain connection for said cylinder, and a solenoid valve controlling said drain and having an energizing circuit controlled by said sensing means.

4. A system providing a stream of fluidised powdered fuel at high pressure comprising, a first fluidising column, means introducing a stream of fluidising air into said column at the bottom thereof, means feeding powdered fuel into said column at substantially atmospheric pressure, a second fluidising column, means including a source of high-pressure air for introducing fluidising air into said second column at the bottom thereof, pumping means for feeding fluidised fuel from said first column into said second column at a pressure substantially higher than atmospheric pressure, flow-control means for varying the rate of flow of fluidised fuel from said first column to said second column, sensing means for sensing the level of fluidised fuel in said second column, and control means controlled by said sensing means and operating said flow-control means to maintain said level within a. predetermined range.

References Cited in the file of this patent UNITED STATES PATENTS 1,616,547 Pontoppidan Feb. 8, 1927 2,668,365 Hogin Feb. 9, 1954 2,675,676 Yellott Aug. 20, 1954 2,716,050 Hagerbaumer Aug. 23, 1955 2,758,564 Randall Aug. 14, 1956 2,763,515 Schutte Sept. 18, 1956 2,770,584 Ray Nov. 13, 1956 

